When Semiconductors Stick Together, Materials Go Quantum

A team of Foundry users has developed a simple method that could turn ordinary semiconducting materials into quantum machines – superthin devices marked by extraordinary electronic behavior. Such an advancement could help to revolutionize a number of industries aiming for energy-efficient electronic systems – and provide a platform for exotic new physics.

The study describing the method, which stacks together 2D layers of tungsten disulfide and tungsten diselenide to create an intricately patterned material, or superlattice, was published online recently in the journal Nature.

Two-dimensional (2D) materials, which are just one atom thick, are like nanosized building blocks that can be stacked arbitrarily to form tiny devices. When the lattices of two 2D materials are similar and well-aligned, a repeating pattern called a moiré superlattice can form.

The new study used 2D samples of semiconducting materials – tungsten disulfide and tungsten diselenide – to show that the twist angle between layers provides a “tuning knob” to turn a 2D semiconducting system into an exotic quantum material with highly interacting electrons.

For light in the energy range that the researchers were considering, they expected to see one peak in the signal that corresponded to the energy of an exciton. Instead, they found that the original peak that they expected to see had split into three different peaks representing three distinct exciton states.

The researchers used a transmission electron microscope (TEM) at NCEM to take atomic-resolution images of the tungsten disulfide/tungsten diselenide device to check how the materials’ lattices were aligned. The images confirmed what they had suspected all along: the materials had indeed formed a moiré superlattice.

The researchers next plan to measure how this new quantum system could be applied to optoelectronics, which relates to the use of light in electronics; valleytronics, a field that could extend the limits of Moore’s law by miniaturizing electronic components; and superconductivity, which would allow electrons to flow in devices with virtually no resistance.